1. Field of the Invention
The present invention relates to a communication node and a communication system. More particularly, it relates to a communication node and a communication system for performing data forwarding, path control, etc. in a network in which a data plane for forwarding user data, and a control plane for managing a data forwarder are made of different media.
2. Description of the Related Art
In recent years, with rise in the speed of a broadband access network, the developments of optical transmission technology have proceeded in order to realize the large-capacity transmission of a trunk network. “GMPLS” (Generalized Multi-Protocol Label Switching) is such that the label switching technique of conventional “MPLS” has been expanded also to an optical wavelength switch. More specifically, the “GMPLS” is a framework in which transmission equipments that adopt different switching techniques such as “PSC” (Packet Switch Capable), “L2SC” (Layer 2 Switch Capable), “LSC” (Lambda Switch Capable), and “FSC” (Fiber Switch Capable) are managed by a common control protocol, and which is configured of a data plane for forwarding user data, and a control plane for managing a data forwarder. The data plane and the control plane are logically separated, and can be made of different physical media.
As a prior-art technique, “RSVP-TE” (Resource ReSerVation Protocol-Traffic Engineering) is one of signaling protocols which are used for controlling a path in the GMPLS (refer to Non-patent Document 1). The “RSVP-TE” reserves resources and establishes an “LSP” (Label Switched Path) in such a way that a “Path” message which holds the ingress and egress of the path, the route thereof, switch sorts, bandwidths and the like attribute information items is propagated along the route on which the path is to be established. Besides, in order to maintain the LSP, refresh messages are exchanged between the adjacent nodes of the control plane at fixed time intervals (refer to Non-patent Document 2).
In addition, as a fault recovery method at the time when any fault has occurred on the GMPLS control plane, there has been proposed a graceful restart scheme in which, even if a controller restarts to lose a path state before the fault, the controller acquires the path state to-be-controlled from the adjacent node at the restart, whereby the path information can be recovered (refer to Non-patent Document 3).
Patent Document 1 discloses a method in which, in order to monitor the states of the data plane and the control plane, an “LSP” has been set by the “RSVP-TE”, a control plane device acquires the route state of the data plane and gives notice to the external network management system of a GMPLS network.
[Non-patent document 1] L. Berger, et al.: IETF RFC3473, “Generalized Multi-Protocol Label Switching (GMPLS) Signaling Resource ReserVation Protocol-Traffic Engineering (RSVP-TE) Extensions”, January 2003 p 1-42
[Non-patent document 2] R. Braden, et al.: IETF RFC2205, “Resource ReSerVation Protocol (RSVP), Version 1 Functional Specification”, September 1997 p 1-112
[Non-patent document 3] A. Satyanarayana, et al.: RFC5063, “Extensions to GMPLS Resource Reservation Protocol (RSVP) Graceful Restart”, October 2007 p1-24
[Patent document 1] JP-A-2008-66989